Human Anatomy Vol 1

UPPEB LIMB

Ulnar nerve and

its superficial

and deep branches

supplying the adjoining sides of the index, middle

and ring fingers.

The lateral common digital branch also supplies

the second lumbrical.

Brqnches

In the hand, the median nerve supplies:

a. Five muscles, namely the abductor pollicis brevis,

the flexor pollicis brevis, the opponens pollicis and

the first and second lumbrical muscles.

b. Palmar skin over the lateral three and a half digits

with their nail beds.

Median nerve and its medial

and lateral divisions

Flexor pollicis brevis

Abductor pollicis brevis

Opponens pollicis

Flexor pollicis longus tendor

Adductor pollicis

Fig. 9.41 : Distribution of the median nerve in the hand. The main divisions of the ulnar nerve are also shown

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o The median nerve controls coarse movements of

the hand, as it supplies most of the long muscles

of the front of the forearm. It is, therefore, called

the labourer's nerue. It is also called "eye of the

hand" as it is sensory to most of the hand.

r When the mediannerve is injured above the level

of the elbow, as might happen in supracondylar

fracture of the humerus, the following features are

seen.

a. The flexor pollicis longus and lateral half of

flexor digitorum profundus are paralysed. The

patient is unable to bend the terminal phalanx

of the thumb and index finger when the

proximal phalanxis held firmlyby the clinician

(to eliminate the action of the short flexors)

(Fig.9.a2). Similarly, the terminalphalarx of the

middle finger can be tested.

b. The forearm is kept in a supine position due to

paralysis of the pronators.

c. The hand is adducted due to paralysis of the

flexor carpi radialis, and flexion at the wrist is

weak.

d. Flexion at the interphalangeal joints of the index

and middle fingers is lost so that the index (and

to a lesser extent) the middle fingers tend to

remain straight while making a fist. This is

called pointing index finger occurs due to

paralysis of long flexors of the digit (Fig. 9.a3).

e. Ape or monkey thumb deformity is present due

to paralysis of the thenar muscles (Fig.9.M).

f. The area of sensory loss corresponds to its

distribution (Fig.9.a5) in the hand.

g. Vasomotor and trophic changes: The skin on

lateral three and a half-digit is warm, dry and

scaly. The nails get cracked easily (Fig. 9.a6).

o Carpal tunnel syndrome (CTS): Involvement of the

mediannerve in carpal tunnel at wrist has become

a very conunon entity (Fig. 9.15).

a. This syndrome consists of motor, sensory/

vasomotor and trophic symptoms in the hand

caused by compression of the median nerve in

the carpal tunnel. Examination reveals wasting

of thenar eminence (ape-like hand), hypn-

aesthesia to light touch on the palmar aspect of

lateral 3r/z diglts. However, the skin over the

thenar eminence is not fficted as the branch of

median nerve supplying it arises in the forearm.

b. Froment's sign/book holding test: The patient

is unable to hold the book with thumb and other

fingers.

c. Paper holding test: The patient unable to hold

paper between thumb fingers.